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gh-87135: Hang non-main threads that attempt to acquire the GIL during finalization (GH-105805)

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Instead of surprise crashes and memory corruption, we now hang threads that attempt to re-enter the Python interpreter after Python runtime finalization has started. These are typically daemon threads (our long standing mis-feature) but could also be threads spawned by extension modules that then try to call into Python. This marks the `PyThread_exit_thread` public C API as deprecated as there is no plausible safe way to accomplish that on any supported platform in the face of things like C++ code with finalizers anywhere on a thread's stack. Doing this was the least bad option.

Co-authored-by: Gregory P. Smith <greg@krypto.org>
This commit is contained in:
Jeremy Maitin-Shepard 2024-10-02 09:17:49 -07:00 • committed by GitHub
parent 113b2d7583
commit 8cc5aa47ee
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GPG key ID: B5690EEEBB952194
10 changed files with 247 additions and 29 deletions
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30
Modules/_testcapimodule.c
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@ -3310,6 +3310,35 @@ test_critical_sections(PyObject *module, PyObject *Py_UNUSED(args))
Py_RETURN_NONE;
}
// Used by `finalize_thread_hang`.
#ifdef _POSIX_THREADS
static void finalize_thread_hang_cleanup_callback(void *Py_UNUSED(arg)) {
// Should not reach here.
Py_FatalError("pthread thread termination was triggered unexpectedly");
}
#endif
// Tests that finalization does not trigger pthread cleanup.
//
// Must be called with a single nullary callable function that should block
// (with GIL released) until finalization is in progress.
static PyObject *
finalize_thread_hang(PyObject *self, PyObject *callback)
{
// WASI builds some pthread stuff but doesn't have these APIs today?
#if defined(_POSIX_THREADS) && !defined(__wasi__)
pthread_cleanup_push(finalize_thread_hang_cleanup_callback, NULL);
#endif
PyObject_CallNoArgs(callback);
// Should not reach here.
Py_FatalError("thread unexpectedly did not hang");
#if defined(_POSIX_THREADS) && !defined(__wasi__)
pthread_cleanup_pop(0);
#endif
Py_RETURN_NONE;
}
static PyMethodDef TestMethods[] = {
{"set_errno", set_errno, METH_VARARGS},
{"test_config", test_config, METH_NOARGS},
@ -3449,6 +3478,7 @@ static PyMethodDef TestMethods[] = {
{"test_weakref_capi", test_weakref_capi, METH_NOARGS},
{"function_set_warning", function_set_warning, METH_NOARGS},
{"test_critical_sections", test_critical_sections, METH_NOARGS},
{"finalize_thread_hang", finalize_thread_hang, METH_O, NULL},
{NULL, NULL} /* sentinel */
};